Air Conditioning Unit with Economizer and Filter Assembly

ABSTRACT

Embodiments of the invention provide an air conditioning (AC) unit including a pre-filter and a water-repellent filter. The water-repellent filter prevents moisture and dirt in the outdoor air from entering the AC unit through depth filtration. The AC unit also includes a vertical partition separating an outside section from an inside section, with a vent allowing air flow between the outside section and the inside section, and an economizer assembly including a damper.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 61/102,688 filed on Oct. 3, 2008, the entire contents of which is incorporated herein by reference.

BACKGROUND

Air conditioning (AC) systems for electrical enclosures can include an economizer assembly to allow circulation of fresh, outdoor air into the enclosures. This can maintain the quality of the indoor air as well as save energy by reducing the work done by a mechanical cooling system.

While current AC systems for larger-sized electrical enclosures use economizers, they require fairly large additional attachments or custom housings to incorporate the economizer assemblies. The increased size of the housing or complicated construction of the additions can greatly increase costs of these AC systems. Therefore, smaller AC systems often do not include an economizer assembly to prevent increased costs of requiring such a large and/or complex footprint to condition a small space.

In addition, conditioned air circulated throughout electrical enclosures not only needs to be cool, but also clean and dry to provide a sufficient operating environment for electronics. Incorporating an economizer assembly to bring in outdoor air requires an opening between the outdoor environment and the inside of the enclosure. Therefore, this poses a risk for moisture and impurities from the outdoor air to enter the enclosure.

SUMMARY

Some embodiments of the invention provide an air conditioning unit for circulating outdoor air into an enclosure. The air conditioning unit includes an economizer assembly, an intake vent allowing outdoor air into the air conditioning unit, and a pre-filter positioned near the intake vent preventing dust and small particles in the outdoor air from entering the air conditioning unit. The air conditioning unit also includes a water-repellent filter positioned downstream from the pre-filter. The water-repellent filter prevents moisture and dirt in the outdoor air from entering the air conditioning unit through depth filtration.

Some embodiments of the invention provide an air conditioning unit including an outside section in communication with the outdoor environment, an inside section in communication with the enclosure, and a vertical partition separating the outside section from the inside section. The vertical partition includes at least one vent allowing air flow between the outside section and the inside section. The air conditioning unit also includes an economizer assembly with a damper coupled to the vertical partition. The damper is capable of substantially covering the at least one vent and temporarily separating the outside section from the inside section.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an AC unit according to one embodiment of the invention.

FIGS. 2A-2E are top, front, bottom, side, and back views of the AC unit of FIG. 1

FIG. 3 is a side cross-sectional view of the AC unit of FIG. 1 while in a mechanical cooling mode.

FIG. 4 is a side cross-sectional view of the AC unit of FIG. 1 while in an economizer cooling mode.

FIG. 5A is a perspective view of an outside section of the AC unit of FIG. 1 while in the mechanical cooling mode.

FIG. 5B is a perspective view of the outside section of the AC unit of FIG. 1 while in the economizer cooling mode.

FIG. 6 is a flow chart illustrating operation of a control system of the AC unit of FIGS. 1-5B.

FIG. 7 is side cross-sectional view of an AC unit according to another embodiment of the invention.

FIG. 8 is a perspective view of an outside section of the AC unit of FIG. 7.

FIG. 9 is a front view of the outside section of the AC unit of FIG. 7.

FIG. 10 is a side cross-sectional view of an AC unit according to another embodiment of the invention.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention.

FIG. 1 illustrates an AC unit 10 according to one embodiment of the invention. The AC unit 10 can be a side-mounted unit used to cool a small building or enclosure that holds electronics for cellular phone towers or similar applications.

In one embodiment, the AC unit 10 can be operated using an input voltage of about 115 volts at a frequency between about 50 Hertz and 60 Hertz and a current between about 16.1 amperes and 21.0 amperes. The AC unit 10 can have a cooling capacity between about 12,000 and 12,500 BTU per hour up to a maximum enclosure temperature of about 131 degrees Fahrenheit. Ambient (outside) operating temperatures for the AC unit 10 can range from about negative 40 degrees Fahrenheit to about 131 degrees Fahrenheit. In other embodiments, the AC unit 10 can be different sizes and include different operating specifications for conditioning air in other spaces, buildings, houses, or enclosures.

FIGS. 1-2E illustrate the exterior of the AC unit 10. In one embodiment, the AC unit 10 can be about 53 inches high, about 15 inches wide, about 12 inches deep, and can weigh about 131 pounds. The AC unit 10 can include an outer housing 12 with an exhaust vent 14, an intake vent 16, a return vent 18, and a supply vent 20 (as shown in FIG. 2E).

FIG. 3 illustrates the AC unit 10 in a mechanical cooling mode. The AC unit 10 can include an outside section (wet side) 22 and an inside section (dry side) 24. The inside section 24 can be adjacent to or in contact with the enclosure, while the outside section 22 can be in contact with the outside (ambient) environment. A back panel 26 of the housing 12 can separate the inside section 24 from the enclosure and a front panel 28 of the housing 12 can separate the outside section 22 from the outside environment. The inside section 24 and the outside section 22 can be separated within the housing 12 by a partition 30.

The outside section 22 can house the exhaust vent 14, the intake vent 16, a compressor 32, a condenser 34, one or more impeller fans 36, a filter 38, and other related components. The other related components can include piping containing refrigerant to be run through the refrigeration cycle. The filter 38 can be a common throwaway fiberglass filter, a washable mesh filter, an electrostatic filter, or another suitable filter. During mechanical cooling, the impeller fans 36 can pull in outdoor air through the intake vent 16, across the filter 38, and release it radially throughout the outside section 22. The air in the outside section 22 can then travel across coils of the condenser 34 and exit the outside section 22 through the exhaust vent 14. As a result, the air passing through the outside section 22 can cool the refrigerant within the condenser coils.

The inside section 24 can house the return vent 18, the supply vent 20, a return fan 40, and an evaporator 42. The return fan 40 (e.g., an impeller fan) can pull air from the enclosure and release it within the inside section 24. The air within the inside section 24 can travel across the evaporator coils and exit the inside section 24 through the supply vent 20. As a result, the air passing across the evaporator coils can be cooled as the refrigerant within the coils is heated, thus supplying cool air to the enclosure. During mechanical cooling, the only components that transfer between the outside section 22 and the inside section 24 can be piping containing refrigerant that circulates through the refrigeration cycle.

The mechanical cooling system can include the elements necessary for a refrigeration cycle, including, but not limited to, the condenser 34, the compressor 32, the evaporator 42, an expansion device (not shown), connective piping, and a liquid to be cycled through the system (e.g., a refrigerant). The refrigerant, at low pressure and in liquid form, cycles through the evaporator coils 42 absorbing heat from passing return air, resulting in the warm return air being cooled and the refrigerant being heated to a vapor at low pressure. The low-pressure, vapor refrigerant reaches the compressor 32, which increases the pressure of the vapor. The high-pressure, high-temperature vapor travels through the condenser coils 34 and is cooled by outside air flowing across the coils, causing the vapor to condense. The cooled, high-pressure liquid reaches the expansion device, which reduces the pressure, continuing to cool the liquid. Finally, the cool, low-pressure liquid again reaches the evaporator coils 42 to complete the cycle and cool the return air. Modifications and alterations of the refrigeration cycle can be made in some embodiments.

FIG. 4 illustrates the AC unit 10 in an economizer cooling mode. In this mode, air can pass between the outside section 22 and inside section 24 via an inside-to-outside (IO) vent 44 and an outside-to-inside (OI) vent 46 in the partition 30. A damper 48 can be positioned to allow up to 100% return air to be released from the inside section 24, through the IO vent 44, to the outside section 22, and through the exhaust vent 14 to the outside environment. Outside air from the intake vent 16 can flow through the OI vent 46, into the inside section 24, and through the supply vent 20 into the enclosure. The direction of air flow is indicated by arrows in FIGS. 3 and 4. In some embodiments, the IC vent 44, the OI vent 46, and the damper 48 can create an economizer assembly of the AC unit 10. In other embodiments, other components capable of allowing outside air to be supplied into the enclosure can be included as an economizer assembly in the AC unit 10.

Mechanical cooling of the return air is generally unnecessary in the economizer cooling mode because all return air is exhausted outside. As a result, refrigerant does not need to be cycled through piping and the compressor 32 can be disabled, thus saving energy. In some embodiments, economizer cooling can either be 100% on, or 100% off, meaning only economizer cooling or only mechanical cooling can be operating at one time.

The damper 48 can control the IO vent 44 between return air and exhausted air, as well as the OI vent 46 between outdoor air and supply air. Rather than the multiple dampers used in conventional economizer assemblies, the single damper 48 of the AC unit 10 can control return air, outdoor air, exhaust air, and supply air. Further, the single damper 48 can be incorporated into the AC unit 10 without requiring a custom assembly or adding to the overall height and footprint of a standard unit. The AC unit 10 can be a standard-sized air conditioning unit with energy-conserving economizer functionality.

As shown in FIGS. 3 and 4, in some embodiments, the damper 48 can be controlled by a crank arm actuator assembly 50. When the AC unit 10 is in economizer cooling mode, a damper motor (not shown) can rotate the crank arm, which can rotate the damper 48 to the position shown in FIG. 4 to allow air to pass through the IO vent 44 and OI vent 46. The damper motor can be controlled by a control system 52, as also shown in FIGS. 3 and 4.

FIGS. 5A and 513 illustrate the AC unit 10 with the front panel 28 removed in mechanical cooling mode and economizer cooling mode, respectively. As shown in FIGS. 5A and 5B, the impeller fans 36 can be positioned vertically above one another. One of the impeller fans 36 (e.g., the top impeller fan 36) can be coupled to a mounting bracket 54 so it is positioned horizontally in front of the other impeller fan 36. The mounting bracket 54 of the upper impeller fan 36 can provide a duct 56 for the lower impeller fan 36. This vertical and horizontal staggered positioning can allow the impeller fans 36 to operate near each other and minimize any negative performance effects of having two impeller 36 fans located in the same air space. The impeller fan 36 positioning can also increase the overall performance of each impeller fan 36. In addition, this multiple-fan configuration can offer improved failsafe operation over single-fan assemblies. For example, if one impeller fan 36 fails, the AC unit 10 can remain in operation using the other impeller fan 36. In the event that the upper impeller fan 36 fails, the duct 56 can help minimize recirculation of the outside air.

In some embodiments, the AC unit can include a dry bulb economizer assembly, in which the control system 52 controls the economizer assembly based on sensed temperatures. In other embodiments, the AC unit 10 can include an enthalpy economizer assembly, in which the economizer cooling mode is controlled based on air enthalpy in addition to temperature. For example, outside air enthalpy can be measured to determine if the economizer cooling mode is sufficient for ventilating the enclosure. This can be accomplished using an outside air enthalpy sensor and/or an inside air enthalpy sensor, as well as outside air and inside air temperature sensors. The outside air enthalpy and temperature sensors can be placed along the outer housing 12 in order to retrieve an accurate representation of the outside air enthalpy and temperature. For example, the outside sensors can be placed a substantial distance from the exhaust vent 14, because sensing the enthalpy of air from the exhaust vent would not give an accurate representation of the outside air. Inside air enthalpy and temperature sensors can be placed either inside the enclosure near the return vent 18 or within the AC unit 10 directly in line with return air in order to retrieve an accurate representation of inside air enthalpy and temperature. The control system 52 can determine the outside and/or inside air enthalpies, as well as compare the outside and inside air temperatures to determine whether outdoor air can be used to cool the enclosure in place of mechanical cooling. The control system 52 can then control the damper motor accordingly to adjust the position of the damper 48.

In one embodiment, inputs to the control system 52 can include inside air temperature, outside air temperature, and outside humidity, as shown in the flow chart of FIG. 6. The control system 52 can first determine (at step 58) outside and inside temperatures (e.g., from temperature sensors). The control system 52 can then compare (at step 60) the inside and outside temperatures. If the inside temperature is about 15 degrees Fahrenheit less than the outside temperature, the control system 52 can proceed to step 62 and enter or continue in the mechanical cooling mode. If not, the control system 52 can proceed to step 64. The control system 52 can determine (at step 64) outside humidity (e.g., from a humidity sensor). If the outside humidity is greater than 60%, as determined at step 66, the control system 52 can proceed to step 68 and enter or continue in the mechanical cooling mode. If not, the control system 52 can proceed to step 70 and enter the economizer cooling mode.

While in the economizer cooling mode, following step 70, the control system 52 can again determine (at step 72) outside and inside temperatures. The control system 52 can again compare (at step 74) the inside and outside temperatures. If the inside temperature is about 10 degrees Fahrenheit less than the outside temperature, the control system 52 can proceed to step 76 and enter the mechanical cooling mode. If not, the control system 52 can proceed to step 78. At step 78, the control system 52 can again determine outside humidity. If the outside humidity is greater than 60%, as determined at step 80, the control system 52 can proceed to step 82 and enter the mechanical cooling mode. If not, the control system 52 can continue in the economizer cooling mode and return to step 72.

If the outside humidity exceeds 60%, the control system 52 can operate the AC unit 10 in the mechanical cooling mode regardless of the measured temperature differences. Also, other temperature and humidity limits can be used in some embodiments. Outputs from the control system 52 can include signals to control the damper motor (to change between the mechanical cooling mode and the economizer cooling mode, or vice versa) and signals to control fan motors (while in the mechanical cooling mode, as described below). In some embodiments, the control system 52 can monitor the recovery rate of the inside temperature in the enclosure. If the AC unit 10 in the economizer cooling mode has not sufficiently cooled the enclosure at a desired rate, the control system 52 can switch to the mechanical cooling mode.

The control system 52 can also control fan motors for the impeller fans 36, 40. The AC unit 10 can be used to cool electrical enclosures (where the inside of the enclosure is a dry, clean environment). Positioning the control system 52, fan motors, and damper motor in the inside section 24 where they are not in contact with humid, ambient air can reduce the cost and/or increase the life of the motors. In addition, if the enclosure is sufficiently cool, mechanical cooling can be slowed as less refrigerant needs to be circulated through the refrigeration cycle The control system 52 can vary the speed of the fan motors controlling the fans 36, 40. This can also reduce noise emitted by the fans 36, 40. In some embodiments, the control system 52 can include a proportional-integral-derivative (PID) controller to control the fan motors and the damper motor based on temperatures and/or enthalpies.

As shown in FIGS. 1-5B, the AC unit 10 can be compact while still utilizing energy-conserving economizer functionality. Unlike conventional AC units with economizers, the economizer assembly can fit into a standard AC unit mounting foot print. The single inside/outside compartment separated by the partition 30, as shown in FIGS. 1-5B (rather than distinctly separate compartments in conventional AC units), can greatly reduce the foot print of the AC unit 10. This can allow AC units 10 for smaller enclosures to include economizer assemblies without a large or complex custom assembly. In addition, smaller AC units 10 can include only one impeller fan 30 to potentially further reduce the footprint.

FIGS. 7-9 illustrate the AC unit 10 according to another embodiment of the invention. The AC unit 10 of FIGS. 7-9 can include the staggered impeller fans 36 and the control system 52 to vary fan speed as described above. However, the AC unit 10 of FIGS. 7-9 only includes a mechanical cooling option. The AC unit 10 of FIGS. 7-9 can have a similar footprint to the AC unit 10 of FIGS. 1-5B, but the partition 30 of the AC unit 10 in FIGS. 7-9 can completely separate the outside section 22 from the inside section 24.

FIG. 10 illustrates the AC unit 10 according to another embodiment of the invention. As shown in FIG. 10, the AC unit 10 can include an additional shroud 84 on the front panel 28, and a first air filter (pre-filter) 86 followed by a water-repellant filter 88 at the intake vent 16. The additional shroud 84 can be an add-on to existing AC units. The positioning of the shroud 84 can allow for convenient installation, removal, and maintenance of the filters 86, 88. The pre-filter 86 can be positioned in front of the water-repellant filter 88 to prevent dust particles or debris from entering the AC unit 10. The pre-filter 86 can be a throwaway fiberglass filter, a washable mesh filter, an electrostatic filter, etc. In addition, the pre-filter 86 can substantially prevent debris from contacting the water-repellant filter 88. The water-repellant filter 88 can be directly downstream from the pre-filter 86 and can be a mechanical filter that includes a hydrophobic media throughout the depth of the filter 88. As opposed to surface filtration, moisture can be continuously removed as air passes throughout the depth of the filter 88. This two-filter assembly can substantially prevent dust and other contaminants from entering the clean environment within the enclosure, as well as substantially prevent moisture within the ambient air from entering the enclosure.

FIG. 10 also illustrates louvers 90 on the sides and front of the shroud 84, as an extension of the exhaust vent 14, causing air to exit out the sides of the AC unit 10. This altered direction of air flow can help ensure that the intake vent 16 is taking in fresh, cool air from the outdoor environment rather than warm, exhausted air from the enclosure.

It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein. Various features and advantages of the invention are set forth in the following claims. 

1. An air conditioning unit for circulating outdoor air into an enclosure, the air conditioning unit comprising: an economizer assembly; an intake vent allowing outdoor air into the air conditioning unit; a pre-filter positioned near the intake vent substantially preventing dust and small particles in the outdoor air from entering the air conditioning unit; and a water-repellent filter positioned downstream from the pre-filter, the water-repellent filter substantially preventing moisture and dirt in the outdoor air from entering the air conditioning unit through depth filtration.
 2. The air conditioning unit of claim 1 and further comprising at least two impeller fans pulling the outdoor air across the pre-filter and the water-repellent filter.
 3. The air conditioning unit of claim 1 and further comprising a shroud removably coupled to the air conditioning unit, the shroud housing the pre-filter, and the water-repellent filter.
 4. The air conditioning unit of claim 3 and further comprising louvers on the shroud directing air out of the air conditioning unit.
 5. The air conditioning unit of claim 1 wherein the air conditioning unit is side-mounted to the enclosure.
 6. An air conditioning unit for cooling an enclosure in an outdoor environment, the air conditioning unit comprising: an outside section in communication with the outdoor environment; an inside section in communication with the enclosure; a vertical partition separating the outside section from the inside section, the vertical partition including a vent allowing air flow between the outside section and the inside section; and an economizer assembly including a damper coupled to the vertical partition, the damper capable of substantially covering the vent and temporarily separating the outside section from the inside section.
 7. The air conditioning unit of claim 6 wherein the damper is rotatable.
 8. The air conditioning unit of claim 6 and further comprising an actuator crank arm assembly controlling the damper.
 9. The air conditioning unit of claim 8 and further comprising a control assembly controlling the actuator crank arm assembly.
 10. The air conditioning unit of claim 9 wherein the control assembly is positioned within the inside section.
 11. The air conditioning unit of claim 6 and further comprising at least one impeller fan positioned in the inside section.
 12. The air conditioning unit of claim 6 and further comprising two impeller fans positioned in the outside section, wherein the two impeller fans are staggered in the vertical direction and the horizontal direction.
 13. The air conditioning unit of claim 6 wherein the air conditioning unit is side-mounted to the enclosure.
 14. An air conditioning unit for an enclosure located in an outside environment, the air conditioning unit comprising: an inside section in communication with the enclosure; an outside section in communication with the outside environment, the outside section adjacent to the inside section and separated from the inside section by a partition; and at least two outside impeller fans positioned in the outside section, the at least two outside impeller fans staggered in the vertical direction and the horizontal direction.
 15. The air conditioning unit of claim 14 wherein the at least two outside impeller fans are coupled to the partition.
 16. The air conditioning unit of claim 14 wherein the partition includes at least two vents providing openings between the outside section and the inside section; and further comprising an economizer assembly including a damper to modulate the openings of the at least two vents.
 17. The air conditioning unit of claim 16 and further comprising an outside intake vent allowing ambient air into the air conditioning unit; and a filter filtering the air entering the outside intake vent.
 18. The air conditioning unit of claim 14 and further comprising at least one inside impeller fan positioned in the inside section.
 19. The air conditioning unit of claim 18 and further comprising a control assembly modulating the speed of the at least two outside impeller fans and the at least one inside impeller fan.
 20. The air conditioning unit of claim 19 wherein the control assembly is positioned within the inside section. 